This invention relates to input devices for computers and, more particularly, to a stylus type input device that incorporates means for inputting right and left mouse button control signals to a computer.
Touch screens are widely used as input devices for computers and are broadly classified according to how they sense touches. Resistive matrix-touch screens typically comprise a transparent plastic membrane that overlays a glass substrate. Too and bottom layers are patterned with parallel metal wires that are perpendicularly aligned to form a grid. Pressing on the top membrane forces the wires together to register a touch.
Resistive analog touch screens are constructed like resistive matrix screens, but are not etched to define a wire grid. Instead, the entire surface acts as one large active area sensor. Touches are registered by measuring voltage dividers in the X and Y directions. Support circuits alternately apply voltage across bus bars on opposite sides of one layer (usually the bottom), first in the X direction and then in the Y direction. When the tap layer contacts the bottom, acts as a probe and measures the X and Y voltage components. These values define the location of the touch point.
In the past, resistive membrane touch screens have been most often used for dedicated applications, such as public access kiosks or manufacturing process control, where the basic interaction is selection from a small set of icons or other targets. In this case, it is sufficient to select an icon as soon as it is touched, or perhaps touched and released. A typical software strategy is for the touch screen device driver to interact with the normal mouse device driver to generate emulated mouse button changes, in accordance with the state of the screen contact. Usually, several emulation options are provided. This is generally satisfactory for a dedicated program, especially if the underlying operating system is hidden from the user.
Now, however, resistive screens, often equipped with a stylus, are increasingly being installed in general purpose computers. For this case, both the operating system and most standard application programs are designed to be controlled by a two-button mouse input device. In such configurations, it is difficult to provide a consistent and intuitive mouse button emulation that allows the touch screen to be used in place of a mouse or other pointing device. As an example, most operations require an ability to drag a cursor to some particular place, and then to start an operation, either by clicking a button (e.g., for a selection of a menu item), or by depressing it and holding a button (e.g., a window drag).
Most of these operations fail if the button is pressed before the cursor is properly positioned. It is then difficult to emulate the left button, using only the touch screen contact signal, without resorting to awkward procedures. For example, one such procedure is to emulate a left-button actuation if no motion occurs after one second. Such a gesture technique is hard to use reliably. The Windows operating system (Windows is a registered trademark of the Microsoft Corporation) also uses the right button, for example, to open special menus. This action can be emulated by more complex procedures involving multiple taps and/or gestures. In addition to being awkward, such procedures may be misinterpreted and cause unintended effects.
Lastly, special difficulties arise when a stylus is used for handwritten inputs. Here it is essential to use the contact signal to segment the handwriting rather than for mouse button emulation.
The prior art, for example, U.S. Pat. No. 4,814,552 to Stefik et al. employees a stylus system using both ultrasonic and infrared transducers. The transducers are used in combination to determine stylus tip location by timing the arrival of ultrasonic signals from the stylus. In addition, the infrared transducers are used to transmit to an associated computer the state of a stylus contact switch and two push buttons.
The use of a wireless link to transmit the button state is essential, as a stylus with connecting wires is clumsy to use. It is preferable, however, to sense position with a resistive touch screen, as such screens are the dominant technology for flat panel displays. As such, they are available at low cost, can be used with fingers as well as with styli, and provide an inherent contact signal with negligible displacement so that the computer can segment handwriting into strokes. In contrast, stylus contact switches often require significant longitudinal displacement for actuation. This can produce segmentation artifacts when used for handwriting, for example noticeable xe2x80x9chooksxe2x80x9d at the end of some strokes.
A further problem with the prior art is that it does not deal with a situation which can arise if the stylus is withdrawn from sensing range at a time when a pushbutton is depressed. The button will then appear to be pressed even if it is later released. This will effectively disable the operating system and/or application programs unless some provision is made to reset the button state.
Accordingly, it is an object of this invention to provide a stylus input device with the capability to input right and left mouse button signals.
It is another object of this invention to provide a stylus, having no direct wire connection to the computer, with an ability to input right and left mouse button control input signals.
It is yet another object of this invention to provide a stylus, having no direct wire connection to a computer, with an ability to input at least one button control signal to the computer, and to clear the signal in the event that the wireless link fails while a button is actuated.
The invention is embodied in a wireless stylus that incorporates, for example, an infrared emitter for communicating with a receiver associated with a computer. The stylus is provided with push-buttons near its tip that can be actuated by the user when the stylus is in the range of a wireless detection sensor. Accordingly, by the combined actuation of the touch screen and a concurrent actuation of one or more of the push buttons, a mouse input to the computer is accomplished.